Various different configurations of brush roller accessories for vacuum cleaners or other floor cleaning devices are known in the art. Such brush roller accessories typically include a housing, one or more main support rollers or running rollers, or glide elements that roll or glide along the floor so as to support much of the weight of the accessory, as well as a power-driven brush roller that brushes the carpet or other floor surface in order to loosen or lift dust, dirt particles, and other soiling agents from the floor, so that these materials can be more effectively sucked away by the vacuum or suction air flow that is applied to the housing through a vacuum cleaner hose and wand assembly, for example.
It is known in the art to provide various mechanical arrangements, whereby the position of the brush roller relative to the floor, and particularly the downward protrusion of the brush roller, can be adjusted to adapt the brushing performance to different carpet pile heights or the like. Such stepped or fixed mechanical settings of the adjusted position of the brush roller are problematic, however, because they are subject to operator error in selecting the wrong adjustment height for the particular operating conditions, and because they do not provide an automatic or responsive adaptation to the prevailing conditions, such as the carpet pile height, the resiliency or cushioning effect of a carpet pad or the like arranged below the carpet, progressive wear of the bristles of the brush roller, and other operating conditions. Thus, such mechanical adjustments of the brush roller do not achieve a constant or responsively adapted contact force or pressure of the brush roller against the carpet or other floor surface being cleaned.
It is also known in the art to provide electrical or electronic adjustment mechanisms to carry out an adjustment of the brush roller so as to achieve a uniform contact or pressing force of the brush roller against the carpet or other floor surface, independent of the underlying floor surface conditions or other operating conditions. Such electrical and electronic adjustment mechanisms, however, are relatively complicated, costly, and prone to malfunction and breakdown.